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PubMed2003

Adaptation in a revised inner-hair cell model.

A revised computational model of the inner-hair cell (IHC) and auditory-nerve (AN) complex was recently presented [Sumner et al., J. Acoust. Soc. Am. 111, 2178-2188 (2002)]. One key improvement is that the model reproduces the rate-intensity functions of low- (LSR), medium- (MSR), and high-spontaneous rate (HSR) fibers in the guinea-pig. Here we describe the adaptation characteristics of the model, and how they vary with model fiber type. Adaptation of the revised model for a HSR fiber is in line with an earlier version of the model [Meddis and Hewitt, J. Acoust. Soc. Am. 90, 904-917 (1991)]. In guinea-pig, poststimulus time histograms (PSTH) have been found to show less adaptation in LSR fibers. Evidence from chinchilla suggests that this is due to chronic adaptation resulting from short interstimulus intervals, and that fully recovered LSR fibers actually show more adaptation. However, the model is able to account for both variations of PSTH shape when fully recovered from adaptation. Interstimulus interval can also affect recovery in the model. The model is further tested against data previously used to evaluate models of AN adaptation. The tests are (i) recovery from adaptation of spontaneous rate and (ii) the recovery of response to acoustic stimuli ("forward masking"), (iii) the response to stimulus increments and (iv) decrements, and (v) the conservation of transient components. A HSR model fiber performs similarly to the earlier version of the model. However, there is considerable variation in response to increments and decrements between different model fibers.

Acoustic Stimulation↗

PubMed1979

Relationship between adaptation and the percept and transformations of stop consonant voicing: effects of the number of repetitions and intensity of adaptors.

Important issues in selective adaptation research concern the relative contribution of response related (perceptual) and stimulus related (acoustic) effects of the adaptor in the adaptive process. Two response related issues pertain to the effects of the adaptor percept and verbal transformations on adaptation. This investigation systematically examined perceptual and acoustic contributions of the adaptor on the adaptation of the voicing feature. Subjects rated the degree of voicing/voicelessness of end-point VOT adaptors, i.e., 5- and 55-ms VOT, and an acoustically neutral adaptor, i.e., 25-ms VOT, during periods of repetitions. The number of adaptor repetitions during each of ten trials was either 5, 32, or 95, and the intensity of the adapting stimulus was either 50, 70, or 90 dB SPL. The major findings were as follows: (1) No significant correlations were found between ratings of voicing percept of the adaptor and magnitude of boundary shift; (2) Increases in repetitions and relative intensity level of end-point adaptors produced significantly greater phonetic boundary shifts and generally greater affects on ratings of test stimuli; and (3) The end-point adaptors produced significant shifts in rating of boundary and nonboundary stimuli. The findings indicate that neigher the adaptor percept or verbal transformations affected the magnitude of adaptation. These results and those for acoustic parameters strongly suggest an acoustic as opposed to a phonetic basis of adaptation of the voicing feature. Furthermore, the effects of end-point adaptors on boundary and nonboundary stimuli support the generalized change in feature sensitivity assumed by a fatigue model of adaptation.

Acoustic Stimulation↗

PubMed1993

Focused attention during selective adaptation along a place of articulation continuum.

The current investigation manipulated subjects' attention to adaptor tokens in five selective adaptation experiments. All stimuli were synthetic consonant-vowel syllables, with the consonant varying from [b] to [d] by formant frequency transitions. Two distractor conditions (auditory and visual) were compared to a more typical endpoint-[d alpha] adaptor condition. Distraction from endpoint-[d alpha] adaptors to phonetically distinct [si] and [integral of i] was used to observe whether smaller adaptation effects would result when attention was not focused on adaptor stimuli. In contrast, a focused attention condition required subjects to whisper [b alpha] adaptors right after they were heard. Performance in the focused attention condition was compared to a more typical endpoint-[b alpha] adaptation condition. Results indicated that focused attention did not affect the size of the adaptation effect. Asymmetrical adaptation results for [d alpha] vs [b alpha] adaptors, and a larger amount of adaptation with the presence of contralateral "distractor" syllables, resembled findings in psychoacoustic studies of discrimination and loudness adaptation. These results suggest that two levels of auditory processing (not special to speech perception) were responsible for the observed adaptation effects.

Acoustic Stimulation↗

PubMed1996

In vitro characterization of aminoglycoside adaptive resistance in Pseudomonas aeruginosa.

Aminoglycoside adaptive resistance was characterized in one reference strain and four clinical isolates of Pseudomonas aeruginosa. Adaptive resistance was initiated with a 2-h gentamicin or tobramycin exposure at the MIC. Each P. aeruginosa strain demonstrated an adaptive-resistance period of between 8 and 12 h when tested with both aminoglycosides. Aminoglycoside adaptive resistance was shown to correlate with a decrease in [3H] gentamicin accumulation and a small (5%) but significant (P < 0.05) reduction in proton motive force. The mean generation time of P. aeruginosa during peak levels of adaptive resistance (i.e., maximum reductions in aminoglycoside killing) was not significantly different from that of control organisms (P < 0.05). No changes in outer membrane protein or lipopolysaccharide sodium dodecyl sulfate-polyacrylamide gel electrophoresis profiles were noted when control, adaptively resistant, and postadaptively resistant cells were compared. Cytoplasmic membrane profiles of adaptively resistant cells, however, demonstrated several band changes when compared with control and postadaptively resistant cells. We conclude that the decrease in aminoglycoside accumulation associated with adaptive resistance in P. aeruginosa may be, in part, a function of reductions in proton motive force and/or cytoplasmic membrane protein changes. However, the importance of these changes requires further investigation.

Anti-Bacterial Agents↗

PubMed1983

Adaptation of natural microbial communities to degradation of xenobiotic compounds: effects of concentration, exposure time, inoculum, and chemical structure.

Adaptation of microbial communities to faster degradation of xenobiotic compounds after exposure to the compound was studied in ecocores. Radiolabeled test compounds were added to cores that contained natural water and sediment. Adaptation was detected by comparing mineralization rates or disappearance of a parent compound in preexposed and unexposed cores. Microbial communities in preexposed cores from a number of freshwater sampling sites adapted to degrade p-nitrophenol faster; communities from estuarine or marine sites did not show any increase in rates of degradation as a result of preexposure. Adaptation was maximal after 2 weeks and was not detectable after 6 weeks. A threshold concentration of 10 ppb (10 ng/ml) was observed; below this concentration no adaptation was detected. With concentrations of 20 to 100 ppb (20 to 100 ng/ml), the biodegradation rates in preexposed cores were much higher than the rates in control cores and were proportional to the concentration of the test compound. In addition, trifluralin, 2,4-dichlorophenoxyacetic acid, and p-cresol were tested to determine whether preexposure affected subsequent biodegradation. Microbial communities did not adapt to trifluralin. Adaptation to 2,4-dichlorophenoxyacetic acid was similar to adaptation to nitrophenol. p-Cresol was mineralized rapidly in both preexposed and unexposed communities.

Journal Article↗

PubMed1984

Interacting effects of hypoxia adaptation and acute hypercapnia on oxygen tolerance in rats.

To define the effects of hypoxia adaptation on tolerance to a useful range of O2 pressures, groups of 20 or more rats were exposed to O2 at 1.0, 1.5, 2.0, 3.0, and 4.0 ATA before and after adaptation to an inspired PO2 (PIO2) of 71 Torr for 5 days. Effects of acute hypercapnia on O2 tolerance in hypoxia-adapted rats were also determined by exposing rats to the same O2 pressures with an inspired PCO2 (PICO2) of 60 Torr. In nonadapted rats exposed to O2 at 1.0, 1.5, 2.0, 3.0, and 4.0 ATA, 50% mortality (LD50) occurred at 76.4, 26.8, 17.4, 9.0, and 6.4 h, respectively. LD50 values in O2-CO2 at the same pressures were 77.1, 24.5, 15.6, 3.4, and 1.7 h. Hypoxia-adapted rats had only 20% mortality in O2 at 1.0 ATA, and survivors were killed at 336 h. In O2-CO2 at 1.0 ATA, mortality was 85% with an LD50 at 282 h. LD50 values in hypoxia-adapted rats at O2 pressures of 1.5, 2.0, 3.0, and 4.0 ATA were 63.1, 22.5, 7.9, and 3.8 h, respectively. Corresponding values in O2-CO2 were 29.5, 18.7, 4.9, and 1.9 h. Exposure to O2 at 4.0 ATA caused nearly immediate onset of violent convulsions in hypoxia-adapted rats compared with a 50% incidence of convulsions at 3.2 h in nonadapted rats. These data indicate that hypoxia-adaptation increases pulmonary O2 tolerance but reduces central nervous system (CNS) O2 tolerance. However, the enhanced pulmonary O2 tolerance in hypoxia-adapted rats is greatly diminished when acute hypercapnia is superimposed on O2 exposure.(ABSTRACT TRUNCATED AT 250 WORDS)

Acid-Base Equilibrium↗

PubMed2002

Spike frequency adaptation and neocortical rhythms.

Spike-frequency adaptation in neocortical pyramidal neurons was examined using the whole cell patch-clamp technique and a phenomenological model of neuronal activity. Noisy current was injected to reproduce the irregular firing typically observed under in vivo conditions. The response was quantified by computing the poststimulus histogram (PSTH). To simulate the spiking activity of a pyramidal neuron, we considered an integrate-and-fire model to which an adaptation current was added. A simplified model for the mean firing rate of an adapting neuron under noisy conditions is also presented. The mean firing rate model provides a good fit to both experimental and simulation PSTHs and may therefore be used to study the response characteristics of adapting neurons to various input currents. The models enable identification of the relevant parameters of adaptation that determine the shape of the PSTH and allow the computation of the response to any change in injected current. The results suggest that spike frequency adaptation determines a preferred frequency of stimulation for which the phase delay of a neuron's activity relative to an oscillatory input is zero. Simulations show that the preferred frequency of single neurons dictates the frequency of emergent population rhythms in large networks of adapting neurons. Adaptation could therefore be one of the crucial factors in setting the frequency of population rhythms in the neocortex.

Action Potentials↗

PubMed1979

Functional profile of the isolated uremic nephron: potassium adaptation in the rabbit cortical collecting tubule.

As a renal function declines in patients and experimental animals with chronic renal disease, potassium homeostasis is maintained by a progressive increase in potassium secretion by the surviving nephrons, a phenomenon known as potassium adaptation. To determine the nephron site and the underlying mechanisms responsible for this phenomenon, studies were performed on normal and 75% nephrectomized rabbits maintained on normal or high-potassium diets. Cortical collecting tubules (CCT) were dissected from the normal and remnant kidneys and perfused in vitro in an artificial solution. In normal CCT mean (+/- SE) net K secretion, JK, (peq/cm per s) was 1.26 +/- 0.43 (normal diet) and 3.27 +/- 0.66 (high-K diet). In uremic CCT, JK was 3.55 +/- 0.60 (normal diet) and 6.83 +/- 0.58 (high-K diet). By reducing the dietary intake of potassium in proportion to the reduction of renal mass in these uremic animals, the adaptation in K secretion was prevented (JK: 1.22 +/- 0.40). Transepithelial potential difference was similar in CCT from normal and uremic animals on a normal diet despite the fact that JK was significantly greater in the latter group. However, in both normal and uremic CCT, the increase in JK caused by potassium loading was associated with an increase in luminal negativity. Uremic CCT underwent significant compensatory hypertrophy regardless of the dietary intake or potassium secretory rates. Plasma aldosterone levels were elevated only in the uremic-high potassium rabbits suggesting that a mineralocorticoid effect on the CCT may be exaggerated when potassium loading is superimposed upon decreased excretory capacity. The activity of Na-K ATPase was comparable in normal and uremic CCT from rabbits on either normal or high-K diets indicating that potassium adaptation may occur independently of changes in the activity of this enzyme. Intracellular potassium content measured chemically and by 42K exchange, was not significantly altered in either normal or uremic CCT when dietary potassium intake was increased, despite the fact the JK was increased under these circumstances. These data indicate that the CCT is an important site of potassium adaptation in the surviving nephrons of animals with reduced renal mass. This adaptation is an intrinsic property of the CCT and is expressed in the absence of a uremic milieu. Potassium adaptation by the uremic CCT is not fixed according to the degree of compensatory hypertrophy but varies according to the excretory requirements of the animal. Transepithelial potential difference and circulating aldosterone levels contribute to the adaptation but neither factor can entirely account for the phenomenon. Potassium adaptation by the CCT occurs in the absence of changes in Na-K ATPase activity and intracellular potassium content.

Animals↗

PubMed1998

Symptoms, cognitive functioning, and adaptive skills in geriatric patients with lifelong schizophrenia: a comparison across treatment sites.

OBJECTIVE: Although many geriatric patients with schizophrenia have been referred to nursing home care, little is known about their characteristics. Across nursing home and chronic hospital settings, the authors directly assessed poor outcome geriatric patients with schizophrenia and contrasted their cognitive, symptomatic, and adaptive functioning to that of acutely admitted patients with a better outcome over the lifetime course of the illness. METHOD: The subjects were 97 chronically hospitalized patients with schizophrenia, 37 patients with chronic schizophrenia who lived in nursing homes, and 31 acutely admitted geriatric patients with schizophrenia. These patients were rated with the Positive and Negative Syndrome Scale, tested with a neuropsychological battery, evaluated with the Mini-Mental State examination, and rated on a scale of social and adaptive deficits, the Social Adaptive Functioning Evaluation scale. RESULTS: Each group of patients proved discriminable from the other two: nursing home patients displayed the most severe adaptive deficits, and acutely admitted patients were the least cognitively impaired. Cognitive impairment was the strongest predictor of adaptive deficits for all three groups, and negative symptom differences among the groups were smaller than differences in cognitive impairment. Nursing home patients had the least severe positive symptoms, and the acutely ill and chronic hospital patients did not differ on positive symptoms. CONCLUSIONS: Cognitive impairment is a predictor of both overall outcome and specific adaptive deficits. These data suggest that interventions aimed at cognitive impairment may have an impact on overall functional status. In comparison, positive symptom severity is less strongly correlated with overall adaptive outcome and is uncorrelated with specific deficits in adaptive skills.

Age Factors↗

PubMed1999

ATP reception and chemosensory adaptation in Tetrahymena thermophila.

Micromolar concentrations of adenosine triphosphate (ATP) and its non-hydrolyzable analog &bgr;- &ggr; -methylene ATP are both effective depolarizing chemorepellents in Tetrahymena thermophila. Chemorepellent behavior consists of repeated bouts of backward swimming (avoidance reactions) that can easily be quantified to provide a convenient bioassay for purinergic reception studies. Chemosensory adaptation occurs following prolonged exposure (10 min) to the repellents, and cells regain normal swimming behavior. Adaptation is specific since cells that are behaviorally adapted to either ATP or &bgr;- &ggr; -methylene ATP still retain full responsiveness to the chemorepellents GTP and lysozyme. However, cross adaptation occurs between ATP and &bgr;- &ggr; -methylene ATP, suggesting that they involve the same receptor. Behavioral sensitivity to both ATP and &bgr;- &ggr; -methylene ATP is increased by the addition of Na+, but addition of either Ca2+ or Mg2+ dramatically decreases the response to ATP. These ionic effects are correlated with in vivo ATP hydrolysis, suggesting that divalent ions decrease purinergic sensitivity by activating a Ca2+- or Mg2+-dependent ecto-ATPase to hydrolyze the ATP signal. In vivo [32P]ATP binding studies and Scatchard analysis suggest that the behavioral adaptation is due to a decrease in the number of surface binding sites, as represented by decreased Bmax values. All these changes are reversible (de-adaptation) after 12 min in a repellent-free buffer. Electrophysiological analysis showed that both &bgr;- &ggr; -methylene ATP (10 micromol l-1) and ATP (500 micromol l-1) elicited sustained, reversible depolarizations while GTP (10 micromol l-1) produced a transient depolarization, suggesting that the chemosensory response pathways for ATP and GTP reception may differ. There may be separate ATP and GTP receptors since ATP and GTP responses do not cross-adapt and 'cold' (unlabeled) GTP is not a good inhibitor of [32P]ATP binding. These results suggests that T. thermophila possess high-affinity surface receptors for ATP that are down-regulated during chemosensory adaptation. These ATP receptors may act as chemorepellent receptors to enable T. thermophila to recognize recently lysed cells and avoid a possibly deleterious situation. This is the simplest eukaryotic organism to show an electrophysiological response to external ATP.

Journal Article↗

PubMedDate not supplied

Production of mosquito densonucleosis viruses by Aedes albopictus C6/36 cells adapted to suspension culture in serum-free protein-free media.

Mosquito densonucleosis viruses (MDVs) have the potential for use as biocontrol agents. To facilitate densovirus production, the Aedes albopictus mosquito cell line C6/36 was adapted to two commercially available serum-free protein-free media (SFPFM), Sf-900 II and Drosophila-SFM. Cells adapted more slowly to growth in Sf-900 II medium, but once adapted, they grew more rapidly and appeared healthier than cells growing in Drosophila-SFM. Cells that were adapted to growth in each of these SFPFM were tested for their ability to be transfected and infected with MDVs. The Sf-900 II-adapted cell line survived transfection and showed infection rates comparable with cells growing in L15 supplemented with 10% fetal bovine serum. Cells adapted to Drosophila-SFM were less infectable and did not survive transfection. Cells adapted to each of these SFPFM were adapted to growth in spinner flasks. Cells in Sf-900 II grew substantially better in spinner flasks than cells in Drosophila-SFM media. Cells grown in Sf-900 II could be frozen and, when thawed, could support the production of densonucleosis viruses in spinner flasks.

Aedes↗

PubMed1978

Ear dominance effects in loudness following auditory adaptation.

In recent years there has been much attention to the study of ear differences in the response to auditory stimuli. However, the possibly of ear differences in auditory adaptation effects has apparently not been investigated. The present authors used a monaural heterophonic balance to investigate the adaptation of a 500 Hz adapting tone. Ten subjects were tested in the left ear, ten in the right. Left ear adaptation was 4.20 dB, while right ear adaptation was 12.88 dB (p is less than or equal to .001). Previous differences in binaural adaptation studies could conceivably have been partially influenced by the ear adapted. It is suggested that the possibility of ear differences in loudness adaptation be taken into account in future studies.

Adolescent↗

PubMed1997

Influence of the intensity of NaCl solutions on adaptation degree and recovery time course.

The degree of adaptation and the time course of recovery after adaptation to NaCl solutions of various intensities were examined by magnitude estimation and simple sensory reaction time using a test stimulus of constant intensity. The results show that the degree of adaptation increased with the adapting concentration following a negatively accelerated function. Similarly, all recovery curves were negatively accelerated functions of the recovery time. The relation between the recovery constant (time necessary to attain two-thirds of normal responsivity) and adapting concentration approximates with both criteria more or less a linear function. Thus the recovery constant is a positively accelerated function of the degree of adaptation. The relationship between concentration and degree of adaptation can be approximated by Beidler's equation of taste stimulation, while the time course of recovery can be expressed by an exponential equation that can also be related to Beidler's theory. The two criteria used showed similar deteriorating effects of taste adaptation, indicating that reaction time can also be a useful criterion of the level of sensory responsivity.

Adult↗

PubMed1976

[Altitude adaptation. V. (conclusion). Morbidity and mortality. Literature].

The ability to adapt to extreme conditions is a continously working principle of man's evolution, in a permanent orientation to an optimal equilibrium between man and environment. A paradigm of biological adaptation is the condition of hypoxia at high altitudes, as one of the few environment constellations to which a pure biological and thus genetically based answer could be possible. The majority of adaptations are influenced by technological actions, which partially modify the environment in compensating unfavourable constellations (heating, clothing, housing, etc.). It is discussed, how far the adaptation to high altitudes produces transitory or permanent alterations with reference to constitution, perseverance, cold-sensitivity, diseases, duration of life, fertility, course of pregnancy, adaptations at the organ- and tissue-level, blood-composition, fluid-equilibrium of the body etc., which guarantee the survival of the individual and its successful reproduction with regard to the continuance of a mendel population. The elucidation of the question on genetic determination of features characteristic for high altitude inhabitants is difficult because we know next to nothing about the genetic determination of physiologic parameters. Studies on ethnic marker-genes (Ethiopia, South-America) give no reference to population differences. Remarkable is a striking prevalence of the blood-group O for all populations of high altitudes, but one must consider the effects of isolation in terms of the increase in the homozygote recessive alleles. We can propose, that in the primary settlement at high altitudes a "hard selection" was working, a kind of biological assortation-process from the beginning, which eliminated those individuals, who proved to be (for genetic reasons?) not adaptable. A good example for this are observations of cattle, from which 50% do not develop pulmonary hypertension when exposed to altitude, that means they already have a higher initial fitness. The non-adaptable animals have to be returned to the lowlands. In the F1-generation only 2% of the animals remaining at high altitude, develop "brisket disease". Possibly that means a sort of "out-mendeling" of "pulmonary-hypertension-genes", which may manifest themselves in the condition of hypoxia. Also the good adaptation of llamas is partially due to the fact that the camelids per se possess an outstanding O2 affinity and morphologically different red blood cells, which predispose this species to inhabit high altitudes. Parallel to considerations like these it could be imaginable, that e.g. the indianids of mongoloids in general, are genetically composed as fit to inhabit lowlands as well as highlands, in contrast to caucasoids and negroids. The largest mountain areas of the world (the Andes: 12 X 10(6)), the Himalayas 12 X 10(6)) are inhabited by populations of mongoloid ancestry, for about 10,000 years, a period, which ought to be long enough to make possible genetic specialisation, although it is not yet possible to prove it...

Acclimatization↗

PubMed1975

[Changes in affinity to mucoprotein receptors of influenza A2-strains after mouse adaptation (author's transl)].

The aim of the study was to establish the relationship between mouse-virulence and affinity of influenza A2-viruses to certain naturally occurring mucoprotein receptor substances. Mouse adaptation of 4 egg adapted cloned H2N2-strains, sensitive to RDE-resistant horse serum inhibitor (PSI), and RDE-sensitive chick serum inhibitor (HSI) in the haemagglutination inhibition and neutralisation test (E+-strains) resulted in mouse virulent strains with diminished PSI-sensitivity (M+-strains, (Table 2). Sensitivity to HSI and to the RDE sensitive fraction of PSI was comparatively less affected (Tables 3, 4). In contrast to the original egg-adapted strains there were only minor differences in inhibitor sensitivity between different M+-strains (Tables 2, 3). 4 mouse virulent strains, derived from 3 egg-adapted strains resistant to PSI and HSI (E--strains), either remained unchanged (2) or gained inhibitor sensitivity (2), (Tables 2, 3). Mouse adapted strains resistant to HSI and PSI could also be selected from M+-strains by passage with PSI in embryonated eggs. In general, properties related to mucoprotein affinity of these strains correspond to those of M--strains derived from E--strains. During selection of M--strains by passage with PSI, strains insensitive to PSI but with considerable residual sensitivity to HSI were encountered (Tables 5, 6). Evidence is presented, that strains of intermediate sensitivity can consist of essentially homogenous populations (Figure 1). While egg adapted inhibitor-sensitive strains showed a high, insensitive strains a low affinity to the human erythrocyte membrane, the reverse was true for mouse adapted strains (Figure 2, Talbes 7, 8). On the other hand all inhibitor-insensitive strains proved to have a higher affinity to the mouse and bovine erythrocyte membrane than sensitive strains (Table 9). PSI-sensitivity of one PSI-sensitivity of one PSI-sensitive Hong Kong/1/68 (H3N2)-strain did not change during mouse adaptation. In a second line, passed in suckling mice, PSI-sensitivity decreased below HSI-sensitivity. Changes in respect to erythrocyte affinity were similar to those of H2-strains.

Animals↗

PubMed2004

Indomethacin, but not Helicobacter pylori, inhibits adaptive relaxation in isolated guinea-pig stomach.

Nonsteroidal anti-inflammatory drugs (NSAIDs) and Helicobacter pylori (H. pylori) are major factors in gastritis and peptic ulcer However, the role of NSAIDs and H. pylori infection in dyspepsia remains unclear. Gastric adaptive relaxation may be related to the pathogenesis of functional dyspepsia because the response is often disturbed in dyspeptic patients. In this study, we investigated the effects of indomethacin or H. pylori water extracts on gastric adaptive relaxation. This experiment was performed using the modified method of Desai et al. Isolated guinea-pig stomach in an organ bath was monitored for intragastric pressure and volume. Adaptive relaxation was induced by gastric luminal distention. The effects of indomethacin and H. pylori on gastric relaxation were tested in this system. Indomethacin (> 1 x 10(-5) M) significantly inhibited adaptive relaxation. Indomethacin (> 3 x 10(-6) M) induced gastric relaxation in a dose-dependent fashion. However, aspirin at a concentration sufficient for cyclooxygenase (COX)-1 inhibition did not induce gastric relaxation. Preincubation with N-nitro-L-arginine methyl ester, a nitric oxide (NO)-synthase inhibitor, inhibited indomethacin-induced gastric relaxation. Adaptive relaxation was not affected by H. pylori water extracts. In conclusion, indomethacin inhibited adaptive relaxation via prior gastric relaxation. NO production, but not COX-1 inhibition, may be involved in this effect of indomethacin. H. pylori water extracts may not have direct effects on adaptive relaxation. Inhibition of adaptive relaxation may be one of the major mechanisms underlying NSAID-induced dyspepsia.

Animals↗

PubMed2005

Framework for measuring adaptive knowledge-rich systems performance.

The universe is non repeatable in nature--most of events cannot be prestated and do not repeat themselves. The only way to create systems that are truly useful is to make them adaptive (able to reason by analogy and learn) and rich in knowledge (including common sense knowledge). Adaptive and knowledge-rich health management could get us closer to errorless health care where small incremental adjustments happen all the time preventing occurrence of an error. In the era of adaptive systems we need to have a way to evaluate their performance. Are they truly adaptive? How adaptive are they? Are they accurate enough? Are they fast enough? Are they cost effective? This chapter presents general framework for measuring adaptive knowledge-rich systems' performance and includes among others definitions of adaptiveness factor, britt (a unit of brittleness) and uso-quant (unit of usefulness of a piece of knowledge). Measuring adaptive knowledge-rich systems performance is one of the most important research areas that can have a big pay-off in healthcare now and in the future.

Artificial Intelligence↗

PubMed2001

[Light adaptation of cones in rabbits and guinea pigs.].

OBJECTIVE: During light adaptation of the retina, cone electroretinograms (ERGs) can be obtained. It is known that during light adaptation considerable changes occur in the cone ERGs of man, monkeys and mice. All these species have vascular retinae. In the present study we examined whether the same applies to mammalian species with a limited retinal vasculature (rabbits) or avascular retinae (guinea pigs), and which both have two types of cones but scotopic ERGs with completely different morphology. MATERIAL AND METHODS: ERGs were recorded from anaesthetized rabbits and guinea pigs with corneal electrodes made from steal wire. Copper wire placed in the mouth of the animal served as reference electrode, and a subcutaneous needle as ground. Recordings were amplified 1000-fold, with bandwidth settings at 1-1000 Hz, and fed into a computer via an A/D converter. Corneas were anaesthetized with a topical application of proparacaine, and pupils dilated with topical application of tropicamide. ERGs were elicited with brief (10 msec) light flashes, and the retina light adapted with a steady white background light. RESULTS: The scotopic b-wave is more than twice the amplitude of the a-wave in rabbits, while the scotopic b-wave in guinea pigs is only slightly larger than the a-wave. The b-wave of the cone ERG is twice the amplitude of the cone a-wave in both species. Once a background light has been turned on, the amplitude increases in both species and the process of light adaptation reaches a peak about 10 minutes thereafter. The b-wave implicit time is shortened by light adaptation in rabbits, but not in guinea pigs. Oscillatory potentials are present in guinea pig ERGs when recorded in dark but not when recorded in light. CONCLUSIONS: Mammals that have avascular retinae and which are without long-wavelength cones show evidence of light adaptation of the cone ERG. In guinea pigs the cone ERG increases in amplitude during light adaptation without concomitant shortening of the implicit time. These changes occur at similar rate in rabbits and guinea pigs. The oscillatory potentials in rabbits increase in amplitude but not in guinea pigs. These results suggest that different mechanisms determine the light adaptation of the cone ERG in guinea pigs than in rabbits.

English Abstract↗